Wheel bearing apparatus is used to freely rotationally support a wheel hub to mount a wheel via a double row rolling bearing for a driving wheel type and a driven wheel type. For structural reasons, an inner ring rotation type is adopted for a driving wheel and both inner ring rotation type and outer ring rotation type are adopted for a driven wheel. The wheel bearing apparatus structure is broadly classified into a first through fourth generation type. A first generation type has a wheel bearing with a double row angular contact ball bearing fit between a knuckle, forming part of a suspension, and a wheel hub. A second generation type has a body mounting flange or a wheel mounting flange directly formed on the outer circumference of an outer member. A third generation type has one of the inner raceway surfaces directly formed on the outer circumference of the wheel hub. A fourth generation type has the inner raceway surfaces directly formed on the outer circumferences of the wheel hub and the constant velocity universal joint.
The wheel bearing apparatus is provided with seals to prevent leakage of grease contained within the bearing apparatus and the entry of rain water or dust from outside of the bearing. It is desired that the bearings have a long life due to the maintenance-free tendency of an automobile. Under the circumstances, it has been proved that many troubles are causes based on the bearing seals rather than on peeling or breakage of mechanical parts. Accordingly, it is very important to improve the sealability of the bearing apparatus to extend its life.
Several types of seals that improve sealability have been proposed. One representative example is shown in FIG. 6. This seal 50 has an annular slinger 53 and an annular sealing plate 54 mounted on an inner ring 51 and an outer member 52, respectively. They are arranged opposite toward each other and each of them has a substantially L-shaped cross-section.
The slinger 53 is formed by pressing a steel plate. It includes a cylindrical portion 53a and a standing portion 53b standing from the cylindrical portion 53a. A magnetic encoder 55, made of a rubber magnet, is bonded to the side surface of the standing portion 53b by vulcanized adhesion. The magnetic encoder 55 has N and S poles alternately arranged along its circumference and constructs a rotary encoder to detect wheel speed.
On the other hand, the sealing plate 54 includes a metal core 56 formed by pressing a steel plate. It is press fit into the outer member 52. A sealing member 57 is integrally bonded to the metal core 56 via vulcanized adhesion. The sealing member 57 is made of elastic material such as rubber or synthetic resin and has a side lip 57a, slidingly contacting the standing portion 53b of the slinger 53, and a pair of radial lips 57b, 57c, slidingly contacting the cylindrical portion 53a of the slinger 53. The outer circumference of the sealing member 57 and the standing portion 53b of the slinger 53 are opposite each other via a slight radial gap between the two to form a labyrinth seal 58.
A projected lip 59 is formed on and extends radially outward from the outer circumference of the sealing member 57. The projected lip 59 is formed with an “L” shaped cross-sectional configuration and is adapted to be arranged in a gap “e” between the outer member 52 and the knuckle 60. The lip 59 prevents rain water or muddy water from entering into the bearing through the gap “e” to prevent the generation of corrosion of the bearing. (Japanese Laid-open Patent Publication No. 56579/2003).
In such a prior art seal 50, when the engagement allowance δ between a lip apex 59a of the projected lip 59 is small, as shown in FIG. 7(a), the projected lip 59 is pressed out radially inward of the knuckle 60 after the knuckle 60 has been assembled as shown in FIG. 7(b) if the lip apex 59a is not positioned at an appropriate position. This causes a gap between the outer member 52 and the projected lip 59. Thus, it is not only impossible to assure the sealability between the outer member 52 and the knuckle 60 but it is possible that the projected lip 59 would be damaged.
In addition as shown in FIG. 8(a), the projected lip 59 may not surely contact the knuckle 60 and the outer member 52 at its two points, i.e. at the lip apex 59a and the lip tip 59b if a bent angle θ is not set at an appropriate value. If so, the projected lip 59 would be collapsed and not spread between the end face of the outer member 52 and the knuckle 60 during the assembly of the knuckle 60 is assembled as shown in FIG. 8(b). Thus sealability between the outer member 52 and the knuckle 60 would not be assured.